Question

a 50.0 gram aqueous sample contains 4.3 mg of salt. what is the percent salt by mass in this solution?
\frac{mass of component}{mass of solution}x100% = mass percentage
0.0086%
0.086%
8.6%
0.008599%
question 6
1 pts
current utah law sets a limit of 4.0 percent alcohol by weight (%mass) for beer sold in grocery stores. this amounts to a volume percentage (%vol) of 5.0% alcohol by volume (abv).
using the formula for volume percentage below, calculate the amount of alcohol in 355 ml of beer (12 fluid ounces).
volume percentage = \frac{volume solute}{volume solution}×100%
71 ml
710 ml
177.5 ml
18 ml

Explanation:

Step1: Convert mass of salt to grams

Since \(1\ mg = 0.001\ g\), then \(4.3\ mg=4.3\times0.001\ g = 0.0043\ g\).

Step2: Calculate mass - percentage

The formula for mass - percentage is \(\frac{\text{mass of component}}{\text{mass of solution}}\times100\%\).
Substitute the values: \(\frac{0.0043\ g}{50.0\ g}\times 100\%=\frac{0.0043\times100}{50.0}\% = 0.0086\%\)

for Question 6:

Step1: Rearrange the volume - percentage formula

The volume - percentage formula is \(\text{volume percentage}=\frac{\text{volume solute}}{\text{volume solution}}\times100\%\).
We want to find the volume of solute (alcohol), so we can rewrite it as \(\text{volume solute}=\frac{\text{volume percentage}\times\text{volume solution}}{100\%}\)

Step2: Substitute the given values

The volume percentage (\(\%\text{vol}\)) is \(5.0\%\) and the volume of the solution (beer) is \(355\ mL\).
\(\text{volume solute}=\frac{5.0\times355}{100}= 17.75\ mL\approx18\ mL\)

Answer:

0.0086%